Effect of surface water and underground water drip irrigation on cotton growth and yield under two different irrigation schemes

To investigate the effect of surface water and underground water drip irrigation on cotton yield, dry matter accumulation and nutrients uptake, two consecutive field experiments were conducted. The first experiment (different mixing ratio irrigation) comprised of five ratios of underground water to surface water including; 1:0 (U), 0:1 (S), 1:1 (U:S = 1:1), 1:2 (U:S = 1:2) and 1:3 (U:S = 1:3). Whereas, the second experiment (round irrigation) comprised of eight treatments including: 1:3 (T1), 2:2 (T2), 3:1 (T3), {S:U 3:1 (T4)}, 2:2 {S:U (T5)}, 1:3 {S:U (T6)}, 4:0 (T7) and 0:4 (T8). The average concentration of leaves dry matter after 8th irrigation in different mixing ratio experiment was significantly increased by 131.2% (S), 34.4% (U: S = 1:1), 59.3% (U: S = 1:2), and 93.7% (U: S = 1:3), respectively, relative to U treatment. Likewise, the stem dry matter increased from 48.5 g (U), to 122.2 g (S) and 101.6 g (U:S = 1:3). The soil available N at 0–20 cm after 8th irrigation recorded an average increase rate of 40.1%, 6.6%, 13.5%, and 29.5%, respectively. However, at 20-40cm an average increase rate of 37.4% (S), 7.1% (U: S = 1:1), 20.0% (U: S = 1:2), and 21.9% (U: S = 1:3) were noted (p < 0.05). The highest cotton yield of 6571 kg h-1 was recorded in S treatment compared with the U treatment (5492 kg h-1), U: S = 1:1 (5502 kg h-1), U: S = 1:2 (5873 kg h-1) and U: S = 1:3 (6111 kg h-1). Contrastingly, in round irrigation experiment the highest leaves dry matter at various growth stages were recorded in T8 treatment. For instance, compared with T7 treatment an average increase rate of 50.6% (growth), 100.9% (boll) and 93.3% (boll opening), in stem dry matter were recorded in T8 treatment. Moreover, the concentration of N in round irrigation at 0–20 cm at different growth stages were 83.3±2.8 (growth stage), 79.01±1.84 (boll stage), and 96.16±3.83 (boll opening stage) in T8. Whereas, in T7 the concentration of N was 36.1±5.9 (growth), 54.51±2.81 (boll), and 53.9±3.83 (boll opening) (p < 0.05). Similarly, cotton yield were substantially higher in T8 applied treatment and follows the sequence of T8 > T1 > T4 > T2 > T5 > T3 > T6 > T7. Overall, our findings provide meaningful information to current irrigation practices in water scarce regions. Improving water use efficiency is a viable solution to the water scarcity. Therefore, surface water irrigation is recommended as an effective irrigation strategies to improve cotton yield and growth.

yourself and the reviewers. All those comments are valuable and very helpful for us to improve our manuscript. We extend our great appreciation for taking the time and efforts to provide such insightful guidance. We have taken a complete consideration to all reviewers' comments as well as those suggestions from the editor's and have made the corrections one by one in the revised version of our manuscript. The changes in the revised MS are marked in track change model.
We sincerely hope the revised manuscript will be able to meet the requirement and will be finally accepted to publish on your journal of "PLOS ONE". Of course, we are always available to provide ongoing changes to our manuscript if there is any further request either from you or from the reviews. Below please find the revised manuscript and the responses. Again, thank you and all the reviewers for your kinder assistance and we are looking forward to hearing from you at your earliest convenience. Best wishes Many thanks again On behalf of the all coauthors Sincerely yours,  If the data are held or will be held in a public repository, include URLs, accession numbers or DOIs. If this information will only be available after acceptance, indicate this by ticking the box below. For example: All XXX files are available from the XXX database (accession number(s) XXX, XXX.).
• If the data are all contained within the manuscript and/or Supporting Information files, enter the following: All relevant data are within the manuscript and its Supporting Information files.
• If neither of these applies but you are able to provide details of access elsewhere, with or without limitations, please do so. For example: Data cannot be shared publicly because of [XXX]. Data are available from the XXX Institutional Data Access / Ethics Committee (contact via XXX) for researchers who meet the criteria for access to confidential data.
The data underlying the results presented in the study are available from (include the name of the third party • All relevant data are within the manuscript and its supporting information files ( Zip file). and contact information or URL). This text is appropriate if the data are owned by a third party and authors do not have permission to share the data.

• * typeset
Additional data availability information: Tick here if the URLs/accession numbers/DOIs will be available only after acceptance of the manuscript for publication so that we can ensure their inclusion before publication. mg/kg (boll opening) (p < 0.05). The highest cotton yield of 6571 kg/hm 2 was observed in S

Introduction
Water for irrigation is one of the most limiting factors for future global agricultural development [1,2]. Climate change, and over-exploitation of water resources in arid and semiarid regions of the world are being subjected to severe water shortages [3]. For instance, , in China the arid and semi-arid area occupies 52.5% of China's land area which is mainly distributed in Northwest, Northeast, and North China [4]. To achieve high grain yields in these regions sufficient irrigation is required, as there are no reliable surface water sources for irrigation, groundwater is the main source of water for irrigation. Moreover, to fulfill the inherent irrigation water requirements, about 60% of the water resources including both surface and underground water is used for agriculture purposes. On the other hand, due to significant increase in population, there is competition for fresh water among municipal, industrial and agricultural sectors in several countries in the world especially in China [5]. Consequently, the allocation of fresh water to agriculture sector in these regions substantially decreased [6].
Therefore, improving irrigation efficiencies by introducing new irrigation strategies is the key and effective way to solve the problem of water shortage, ecological environment deterioration, and to develop agricultural production system in arid and semi-arid regions.
Cotton (Gossypium hirsutum L.), an important source of natural fibers for textile industries that serve the humanity from at least more than four to seven thousand years ago [7].
The current global cotton fiber production is estimated to be 24.65 million tons, with 6.71 million tons produced in America, 0.38 million tons produced in Europe, and 15.06 million tons produced in Asia [8]. Following this, only China accounts for one-quarter of the world's cotton output and one-third of the world's cotton consumption [9]. On the flip side, cotton production is completely dependent on irrigation i.e., the shortage of irrigation water resources restricts the comprehensive improvement of cotton productivity [10,11]. On average, water requirements for cotton growth vary from 700 to 1200 mm during the growing season, depending on irrigation method, and production goals [12]. Numerous studies have been conducted to examine water-use efficiency of cotton in recent years. For instance, a study conducted by Grismer [13] noted that, in Arizona counties, for upland cotton actual evapotranspiration (ETc) water-use efficiency varied from 1.27 to 1.38 kg/ha-mm while, for pima cotton, its varied from 0.9 to 1.09 kg/ha-mm.
In California counties, ETc water-use efficiency varied from 1.34 to 2.10 kg/ha-mm and 1.51-1.77 kg/ha-mm for upland and pima varieties, respectively. Furthermore, due to unevenly distribution of annual precipitation across the season, both surface water resources (water from rivers and reservoirs) and groundwater resources (water stored in aquifers) were used for agriculture purposes in arid and semi-arid regions. However, irrigation with underground water has a negative impact on cotton productivity, plant nutritional condition, and dry matter accumulation. For instance, excessive underground water irrigation exacerbates the soil salinization problems, and reduce crop yield [11,14]. Likewise, well water irrigation with low temperature potentially inhibits the growth and development of cotton plant [15]. Moreover, low soil temperatures may slow down the uptake rate of nutrients such as N so much that they turn out to limit vegetative growth rates [16]. Following this at 20°C-RZT, nutrient concentrations have been significantly affected plant growth indexes, indicating that low root temperature inhibited high nutrient effects on plant growth [16,17]. While on the other hand, surface water irrigation shows promising effect on increasing crops yield [18,19]. For example, irrigating seedlings with warm water (surface water) can increase the stem thickness, leaf area, root coefficient, photosynthetic rate, dry matter per unit fresh weight, root-shoot ratio, and strong seedling index of seedlings [16]. Therefore, clarifying the effect of surface water and underground water on cotton growth and yield by applying different irrigation regime is of paramount importance for improving crop productivity under limited water supply.
Xinjiang Uygur Autonomous Region is one of the most water-scarce states in China.
According to the Statistics Bureau of Xinjiang Uygur Autonomous Region, the water production per unit area of Xinjiang Uygur Autonomous Region is 51 mm, which is the second highest rank in the country [19]. The large number of glaciers in Xinjiang Uygur Autonomous Region and the small unit area are important issues of water resources in Xinjiang Uygur Autonomous Region.
Snowmelt water from glaciers accounts for more than 25% of total surface water [20]. However, according to China's statistics, Xinjiang's total cotton output in 2017 was 4.082 million tons, accounting for 74.4% of the country's total production [20]. While on the other side, agriculture in Xinjiang is totally dependent on irrigation, according to 2016 Xinjiang Water Resource Bulletin, agriculture consumes 94.3% of the available total water resources.
In the present-day context, lot of emphasis is being given on improvements in irrigation practices to increase crop production and to sustain the productivity levels. In this study, two field experiments were carried out in calcareous soils. We hypothesize that surface water drip irrigation outcompetes underground water irrigation in increasing cotton yield, dry matter accumulation and NPK uptake. Therefore, the objectives of our study were to (i) compare the effects of different irrigation schemes on cotton growth and yield. (ii) Clarify the response of cotton growth to surface and underground water addition, (iii) finally put forward an appropriate irrigation strategy to increase cotton yield in calcareous soil.

Experimental site
The study area is located in the Mosuowan reclamation region (44°03′N, 86°05′E), which is located on the northern slope of Tianshan Mountain in Xinjiang and is surrounded by the Gurbantunggut Desert. According to WRB soil taxonomy, the tested soil is classified as Calcisol Fluvisols. The study area has a typical continental climate with a mean annual precipitation of 115 mm, and rainfall largely occurs from April to July. The mean annual potential evapotranspiration is approximately 2,000 mm. The physicochemical characteristics of given soil is listed in (Table 1). Table 1. Selected physical and chemical properties of the tested soils.
Data were presented as the mean ± standard error (SE), n=3 at a significance level of p < 0.05. a. pH was determined at soil to milli-Q water ratio of 1:5 w/v using pH meter. b. Organic matter was measured by potassium dichromate volumetric method (Shaw, 1959) [37]. c. Total N was measured by the semimicro-Kjeldahl method (Bao 2000). d. Total P was measured by the perchloric acid digestion method (Bao 2000). e. Total and available K was measured by the flame photometry method (Bao 2000).

Experimental Design
The first experiment (different mixing ratio) was a randomized complete block design (RCBD) field experiment conducted on April 12, 2019 with five treatments including U (underground water); S (surface water); U:S= 1:1; U:S= 1:2; U:S= 1:3, respectively. Each treatment was replicated three times while the area of each block was 55.2 m 2 . For the mixing ratio experiment we dig several whole and cover it with plastic, after that we supply surface and Soil properties 0-20cm pH OM (g kg -1 ) Total-N (g kg -1 ) Available-P (mg kg -1 ) Total-P (g kg -1 ) Total-K (mg kg -1 ) Available-K (mg kg -1 ) underground water into the whole with a constant water ratio by using water ratio measurement instrument. After supplying water we mix the nutrient with the water and supply it to cotton field through drip irrigation. The schematic of our experimental design are presented in supplementary figure 1. The supply of water and nutrients for each irrigation has listed in (Table 2). The second experiment (round experiment) was a field randomized complete block In round water irrigation we supply the constant ration of both surface water and underground water directly to the cotton field at various growth stages without mixing it. For maintaining the required ratios we first supply the specific ratio of surface water and then we supply the specific ratio of underground water by using a water ratio measurement meter. Further details about irrigation is given in (Table 3). Nutrients (fertilizer) and water were supplied through drip irrigation. The supply of water and nutrients for each irrigation has listed in (Table 4). Table 3. Supply of surface and underground water at different growth stage of cotton (round irrigation 2020) Table 4. The supply of water and nutrients (fertilizer) for each irrigation (round irrigation 2020).

Soil and Plants sampling
Soil samples were collected at depths of 0-20 cm and 20-40 cm from each block after 3-5 days of irrigation. Samples were air dried, sieved through 1mm and 0.15 mm for nutrients determination. The pH was determined at soil to milli-Q water ratio of 1:5 w/v using pH meter.
The organic matter was determined by potassium dichromate volumetric method. Nitrogen was determined by semi micro-Kjeldahl method [37]. Phosphorus was measured by the per chloric  [38]. Potassium was determined by flame photometry [37]. Soil available Nitrogen, soil available phosphorus, soil available potassium and soil organic matter were determined in soil samples after growth stage, boll stage and boll opening stage.
Plant samples were randomly collected from each block at interval of 3-5 days after each irrigation. Plant samples were divided into the following parts (leaves, stems, roots and fruits), washed with tap water and then dried in oven at 105˚C for 30 minutes and then at 75˚C for 3 days. The plant samples were then weighed with balance and the dry matter data were calculated after growth stage, boll stage and boll opening stage, following the method of [39] ( Figure 1).

Statistical analysis
Data were analyzed using the SPSS 25.5 statistical program (SPSS Inc., Chicago, IL, USA) with ANOVA at a significance level of p < 0.05. A Duncan multiple range test was carried out to test the significant differences between different treatments. GraphPad Prism 12.0 software (GraphPad Software, Inc., San Diego, CA, USA) was used for data processing and images making. All results in figures and tables were presented as mean ± standard deviation (SD) of three replicates, and a significance level of p <0.05 was used for all analysis.

Effects of different mixing ratio irrigation method on the dry matter accumulation
The average dry matter accumulation in the different parts of the cotton plant fluctuated greatly with different irrigation treatments and increased sharply after each irrigation time

Effects of round irrigation method on dry matter accumulation
Round irrigation method also significantly affected dry matter accumulation in the different parts of the plant at various stages of growth (p < 0.05, Figure.  Insert " (Figure 3)"

Effects of different mixing ratio and round irrigation on soil available nutrients
Soil available nitrogen at a depth of 0-20 and 20-40 cm fluctuated greatly during the whole cotton growth period, and increased sharply after each irrigation time ( Figure. Table 5).
The soil available P content significantly increased in the initial and final stages with T8 treatment throughout the experiment (p < 0.05, Table 6). While, the status of available potassium in soil remains parallel throughout the experiment, the difference between different applied treatments were negligible (p < 0.05, Table 7). However, the maximum concentration of potash was determined in T8 treatment. Soil organic matter was significantly affected by different irrigation treatments (p < 0.05, Table 8). However, at the start of the experiment the surface water irrigation treatment shows promising effect at both 0-20 and 20-40 cm, while the difference between other treatments were negligible.
Insert " (Figure 4 and Figure 5)" Insert " (Table 5, Table 6, Table 7 and Table 8)" Table 5. Effect round irrigation method on soil available nitrogen (mg/kg). Data were presented as the mean ± standard deviation (SD) of three replicates at a significance level of p < 0.05 (based on ANOVA). Table 6. Effect round irrigation method on soil available phosphorus (mg/kg). Data were presented as the mean ± standard deviation (SD) of three replicates at a significance level of p < 0.05 (based on ANOVA).  Table 7. Effect round irrigation method on soil available potassium (mg/kg). Data were presented as the mean ± standard deviation (SD) of three replicates at a significance level of p < 0.05 (based on ANOVA).  Table 8. Effect round irrigation method on soil organic matter (g/kg). Data were presented as the mean ± standard deviation (SD) of three replicates at a significance level of p < 0.05 (based on ANOVA).

Effects of different irrigation methods on cotton yield
The effect of different mixing ratio irrigation on cotton yield is presented in Figure 6a.
Cotton yield responded significantly to different water irrigation modes. For instance, the maximum cotton yield 6571 kg/hm 2 was observed in (S) treatment compared with the treatment (U) (5492 kg/hm 2 ), U: S= 1:1 treatment (5502 kg/hm 2 ), U: S= 1:2 treatment (5873 kg/hm 2 ) and U: S= 1:3 treatment (6111 kg/hm 2 ). Likewise, round irrigation potentially effect cotton yield under different applied treatments (Figure 6b). For example, the increasing trend follow the order of T8 > T1 > T4 > T2 > T5 > T3 > T6> T7, which shows that surface water irrigation can effectively guarantee cotton production. The highest cotton yield was observed in T8 treatment in which surface water was supplied through all stages of cotton growth, followed by treatment T1 and T4 (Figure 6b). However, the lowest yield was recorded in treatment T7 in which underground water was supplied.

Discussion
Xinjiang region is one of the most important cotton producers with the plantation area of about 1.8 × 106 ha, accounting for 54% of China's total cotton planting area [20]. Approximately, about 451 × 104 tons of cotton were produced in 2014, accounting for 73% of China's total cotton production [18]. Meanwhile, surface water evaporation caused by high temperatures results in a severe water shortage in southern Xinjiang leading to soil salinization, a lowered survival rate for crops, and slow development of local agriculture [21]. Similarly, increased usage of underground water for irrigation exacerbates the soil salinization problems, which significantly reduce crop yield [10,11]. In this study, the application of surface water in both mixing ratio and round irrigation methods, significantly promotes dry matter accumulation (  [34,35,36]. The superiority of surface water over underground water in calcareous soil may likely be due to the following reasons; in general surface water possess high temperature while the underground water temperature is quite low. Previous study has shown that well water irrigation with low temperature potentially inhibits the growth and development of jujube [22]. Likewise, several published literatures have shown that underground water irrigation (low temperature water) affect the growth, yield, dry matter accumulation and active developmental stages of grains plants such as peanuts, cucumber, and tomato [23,24,25,26]. For instance, a study conducted by Meng et al. (2016), noted that underground water irrigation significantly affects the growth and development of cotton plant. Similar results with the application of underground water irrigation is also obtained in this study. Furthermore, Deng et al., [27], also pointed out that underground water irrigation along with their low temperature properties significantly retarded the growth of vegetables and their photosynthetic developments.
Consequently, the excessive usage of underground water irrigation results in the accumulation of toxic substances in soil which alternatively leads to reduction in plants and grains yields [28,29].
The accumulation of salt can directly decrease soil nutrient efficiency by inhibiting microbial mineralization activity in soil [30]. Additionally, salinity can also indirectly affect soil nutrient cycling and efficiency by destroying soil physical structure [31,32,33]. On the flip side, the study of Zhang et al., 2002 [34] showed that alternate irrigation with surface fresh water can reduce soil salt content and increase cotton production which are in line with our findings. In this study surface water irrigation along with different mixing ratios irrigation also shows promising effects on cotton yield and dry matter accumulation when compared with underground water treatment alone, this is possibly due to when the underground water and surface water were mixed together, the temperature and salt content were changed. For example, a study conducted by Tao et al. 2014 [35], showed that mixed irrigation mode of brackish and fresh water with a salinity of 1.6g/L could achieve higher crop yield with better quality. Consistently, a study carried out by Wang et al. 2010 [36], showed that well and canal mixed irrigation could keep the salt balance of root soil even in relatively dry years, while well irrigation alone results in salt accumulation in roots of winter wheat and decreased the yield up to 20% -30%. All these findings suggest that under-ground water irrigation possess negative effects on plant yield and growth whilst surface water irrigation and different mixing ratios irrigation significantly promote cotton yield, NPK uptake and dry matter accumulation.

Conclusions
It can be concluded that the application of surface water along with their different mixing ratios irrigation outcompete underground water irrigation in both mixing ratio and round irrigations methods. A significant highest dry mater accumulation, nutrients uptake and cotton yield at various stages i.e., growth stage, boll stage, and boll opening stage were always noted surface water applied treatments compared with underground water treatment. Overall, our findings provide meaningful information to current irrigation practice in increasing cotton growth and yield. Therefore taken into account the scarcity of water resource surface water irrigation application is recommended as an effective irrigation strategy in Xinjiang calcareous soil for better cotton yield and nutrient uptakes.

Disclosure statement
The authors declare that they have no conflict of interest.           represent fruits dry matter, respectively. Data were presented as the mean ± standard deviation (SD) of three replicates at a significance level of p < 0.05. The inserted P values are from two-way ANOVAs.  Experiment I mixing ratio irrigation method; figure (2020) represents Experiment II Round irrigation method. Data were presented as the mean ± standard deviation (SD) of three replicates at a significance level of p < 0.05 (based on two-way ANOVA). Overall, our findings provide useful information to current irrigation practices in water scarce regions. Alternatively, improving water use efficiency is a viable solution to the water scarcity. Therefore, surface water irrigation is recommended as an effective irrigation strategies to Therefore, it is suggested that surface water irrigation should be applied to maximize the cotton yield, dry matter accumulation, nutritional status and overall growth of cotton crop. Keywords:;;; Irrigation strategies; Gossypium hirsutum L; dry matter accumulation; N,P,K, P, K uptake;; underground water.

Introduction
Water for Iirrigation water is one of the most limiting factors for future global agricultural development [1,2]. Climate change, and over-exploitation of water resources in Aarid and semiarid regions of the world are being subjected to severe water shortages due to climate change and over-exploitation of water resources [3]. For instance, Taken China is an example, in China the arid and semi-arid area occupies 52.5% of China's land area which is mainly distributed in Northwest, Northeast, and North China [4]. To achieve high grain yields Agriculture sectors in these regions are totally dependent on sufficient irrigation is required, as there are no reliable surface water sources for irrigation, groundwater is the main source of water for irrigation. Moreover, Tto fulfill the inherent irrigation water requirements, about 60% of the water resources including both surface and underground water is used for agriculture purposes. On the other hand contrast, due to significant increase in population, there is competition for fresh water among municipal, industrial and agricultural sectors in several countries in the world especially in China [5]. Consequently, the allocation of fresh water to agriculture sector in these regions substantially decreased [6]. Therefore, improving irrigation efficienciesy by introducing new irrigation strategies is the key and effective way to solve the problem of water shortage, ecological environment deterioration, and to develop agricultural production system in arid and semi-arid regions.
Cotton (Gossypium hirsutum L.), an important source of natural fibers for to textile industries that serve the humanity from at least more than four to seven thousand years ago [7].
The current global cotton fiber production is estimated to be 24.65 million tons, with 6.71 million tons produced in America, 0.38 million tons produced in Europe, and 15.06 million tons produced in Asia [8]. Following this, only China accounts for one-quarter of the world's cotton output and one-third of the world's cotton consumption [9]. On the flip sideHowever, cotton production is completely dependent on irrigation i.e., the shortage of irrigation water resources restricts the comprehensive improvement of cotton productivity [10,11]. On average, Wwater requirements for cotton growth vary from 700 to 1200 mm during the growing season, depending on irrigation method, and production goals [12]. Numerous studies have been conducted to examine water-use efficiency of cotton in recent years. For instance, a study conducted by Grismer [13] found noted that, in Arizona counties, for upland cotton actual evapotranspiration (ETc) water-use efficiency varied from 1.27 to 1.38 kg/ha-mm while, for pima cotton, its varied from 0.9 to 1.09 kg/ha-mm. In California counties, ETc water-use efficiency varied from 1.34 to 2.10 kg/ha-mm and 1.51-1.77 kg/ha-mm for upland and pima varieties, respectively. Furthermore, due to unevenly distribution of annual precipitation across the season, Bboth surface water resources (water from rivers and reservoirs) and groundwater resources (water stored in aquifers) were used for agriculture purposes in arid and semi-arid regions. However, irrigation with underground water has a negative impact on cotton productivity, plant nutritional condition, and dry matter accumulation. For instance, excessive underground water irrigation exacerbates the soil salinization problems, and reduce crop yield [11,14]. Likewise, well water irrigation with low temperature potentially inhibits the growth and development of cotton plant [15]. Moreover, low soil temperatures may slow down the uptake rate of nutrients such as N so much that they turn out to limit vegetative growth rates [16].
Following this Aat 20°C-RZT, nutrient concentrations have been significantly affected plant growth indexes, indicating that low root temperature inhibited high nutrient effects on plant growth [16,17]. While on the other hand, surface water irrigation shows promising effect on increasing crops yield [18,19]. For example, irrigating seedlings with warm water (surface water) can increase the stem thickness, leaf area, root coefficient, photosynthetic rate, dry matter per unit fresh weight, root-shoot ratio, and strong seedling index of seedlings [16]. Therefore, clarifying the effect of surface water and underground water on cotton growth and yield by applying different irrigation regime is of paramount importance for improving crop productivity by using less waterunder limited water supply.
Xinjiang Uygur Autonomous Region is one of the most water-scarce states in China.
According to the Statistics Bureau of Xinjiang Uygur Autonomous Region, the water production per unit area of Xinjiang Uygur Autonomous Region is 51 mm, which is the second highest rank in the country [19]. The large number of glaciers in Xinjiang Uygur Autonomous Region and the small unit area are important issues of water resources in Xinjiang Uygur Autonomous Region.
Snowmelt water from glaciers accounts for more than 25% of total surface water [20]. However, according to China's statistics, Xinjiang's total cotton output in 2017 was 4.082 million tons, accounting for 74.4% of the country's total production [20]. While on the other side, agriculture in Xinjiang is totally dependent on irrigation, according to 2016 Xinjiang Water Resource Bulletin, agriculture consumes 94.3% of the available total water resources.
In the present-day context, lot of emphasis is being given on improvements in irrigation practices to increase crop production and to sustain the productivity levels. In this study, two field experiments were carried out in calcareous soils. We hypothesize that surface water drip irrigation outcompetes underground water irrigation in increasing cotton yield, dry matter accumulation and NPK uptake. Therefore, the objectives of our study were to (i) compare the effects of different irrigation schemes on cotton growth and yield. (ii) Clarify the response of cotton growth to surface and underground water addition, (iii) finally put forward an appropriate irrigation strategy to increase cotton yield in calcareous soil.

Experimental site
The study area is located in the Mosuowan reclamation region (44°03′N, 86°05′E), which is located on the northern slope of Tianshan Mountain in Xinjiang and is surrounded by the Gurbantunggut Desert. According to WRB soil taxonomy, the tested soil is classified as Calcisol Fluvisols. The study area has a typical continental climate with a mean annual precipitation of 115 mm, and rainfall largely occurs from April to July. The mean annual potential evapotranspiration is approximately 2,000 mm. The physicochemical characteristics of given soil is listed in (Table 1). Table 1. Selected physical and chemical properties of the tested soils.Insert " (Table 1)

"
Data were presented as the mean ± standard error (SE), n=3 at a significance level of p < 0.05. a. pH was determined at soil to milli-Q water ratio of 1:5 w/v using pH meter. b. Organic matter was measured by potassium dichromate volumetric method (Shaw, 1959) [37]. c. Total N was measured by the semimicro-Kjeldahl method (Bao 2000). d. Total P was measured by the perchloric acid digestion method (Bao 2000). e. Total and available K was measured by the flame photometry method (Bao 2000).

Experimental Design
The first experiment (different mixing ratio) was a randomized complete block design (RCBD) field experiment conducted on April 12, 2019 with five treatments including U (underground water); S (surface water); U:S= 1:1; U:S= 1:2; U:S= 1:3, respectively. Each treatment was replicated three times while the area of each block was 55.2 m 2 . For the mixing ratio experiment we dig several whole and cover it with plastic, after that we supply surface and underground water into the whole with a constant water ratio by using water ratio measurement instrument. After supplying water we mix the nutrient with the water and supply it to cotton field through drip irrigation. The schematic of our experimental design are presented in supplementary figure 1. The supply of water and nutrients for each irrigation has listed in (Table 2).  In round water irrigation we supply the constant ration of both surface water and underground water directly to the cotton field at various growth stages without mixing it. For maintaining the required ratios we first supply the specific ratio of surface water and then we supply the specific ratio of underground water by using a water ratio measurement meter. Further details about irrigation is given in (Table 3). Nutrients (fertilizer) and water were supplied through drip irrigation. The supply of water and nutrients for each irrigation has listed in (Table 4). Table 3. Supply of surface and underground water at different growth stage of cotton (round irrigation 2020) 1 U represents the supply of underground water. 2 S represents the supply of surface water.  Table 4. The supply of water and nutrients (fertilizer) for each irrigation (round irrigation 2020).

Plants sampling
Soil samples were collected at depths of 0-20 cm and 20-40 cm from each block after 3-5 days of irrigation. Samples were air dried, sieved through 1mm and 0.15 mm for nutrients determination. The pH was determined at soil to milli-Q water ratio of 1:5 w/v using pH meter. The organic matter was determined by potassium dichromate volumetric method. Nitrogen was determined by semimicro-Kjeldahl method [37]. Phosphorus was measured by the perchloric acid digestion method [38]. Potassium was determined by flame photometry [37]. Soil available Nitrogen, soil available phosphorus, soil available potassium and soil organic matter were determined in soil samples after growth stage, boll stage and boll opening stage.
Plant samples were randomly collected from each block at interval of 3-5 days after each irrigation. Plant samples were divided into the following parts (leaves, stems, roots and fruits),  (Table 2).

Insert "(Table 2)"
The second experiment was a field randomized complete block design (RCBD) having i.e., seedling stage, growth stage, boll stage and boll opening stage. Further details about irrigation is given in (Table 3). Nutrients (fertilizer) and water were supplied through drip irrigation. The supply of water and nutrients for each irrigation has listed in (Table 4).

Soil and Plants sampling
Soil samples were collected at depths of 0-20 cm and 20-40 cm from each block after 3-5 days of irrigation. Samples were air dried, sieved through 1mm and 0.15 mm for nutrients determination. The pH was determined at soil to milli-Q water ratio of 1:5 w/v using pH meter.
The organic matter was determined by potassium dichromate volumetric method. Nitrogen was determined by semi micro-Kjeldahl method [37]. Phosphorus was measured by the per chloric acid digestion method [38]. Potassium was determined by flame photometry [37]. Soil available Nitrogen, soil available phosphorus, soil available potassium and soil organic matter were determined in soil samples after growth stage, boll stage and boll opening stage.
Plant samples were randomly collected from each block at interval of 3-5 days after each irrigation. Plant samples were divided into the following parts (leaves, stems, roots and fruits), washed with tap water and then dried in oven at 105˚C for 30 minutes and then at 75˚C for 3 days. The plant samples were then weighed with balance and the dry matter data were calculated after growth stage, boll stage and boll opening stage, following the method of [39] (Figure 1).

Statistical analysis
Data were analyzed using the SPSS 25.5 statistical program (SPSS Inc., Chicago, IL, USA) with two-way ANOVA at a significance level of p < 0.05. A Duncan multiple range test was carried out to test the significant differences between different treatments. GraphPad Prism 12.0 software (GraphPad Software, Inc., San Diego, CA, USA) was used for data processing and images making. All results in figures and tables were presented as mean ± standard deviation (SD) of three replicates, and a significance level of P p <0.05 was used for all analysis.

Effects of different mixing ratio irrigation method on the dry matter accumulation
The Insert " (Figure 3)"

Effects of different mixing ratio and round irrigation on soil available nutrients
Soil available nitrogen at a depth of 0-20 and 20-40 cm fluctuated greatly during the whole cotton growth period, and increased sharply after each irrigation time ( Figure. 4a, b). The  Table 5).
The soil available P content significantly increased in the initial and final stages with T8 treatment throughout the experiment (p < 0.05, Table 6). While, the status of available potassium in soil remains parallel throughout the experiment, the difference between different applied treatments were negligible (p < 0.05, Table 7). However, the maximum concentration of potash was determined in T8 treatment. Soil organic matter was significantly affected by different irrigation treatments (p < 0.05, Table 8). However, at the start of the experiment the surface water irrigation treatment shows promising effect at both 0-20 and 20-40 cm, while the difference between other treatments were negligible.
Insert " (Figure 4 and Figure 5)" Insert " (Table 5, Table 6, Table 7 and Table 8)" Table 5. Effect round irrigation method on soil available nitrogen (mg/kg). Data were presented as the mean ± standard deviation (SD) of three replicates at a significance level of p < 0.05 (based on ANOVA). Table 6. Effect round irrigation method on soil available phosphorus (mg/kg). Data were presented as the mean ± standard deviation (SD) of three replicates at a significance level of p < 0.05 (based on ANOVA). Insert " (Figure 6)"

Discussion
Water for irrigation is a major limitation to agricultural production in the Xinjiang region.
The Xinjiang region in Northwest China is one of the most important cotton producers with the .
The cotton plantation area ofin Xinjiang is about 1.8 × 106 ha, accounting for 54% of China's total cotton planting area [20]. Approximately, aboutIt produced 451 × 104 tons of cotton were produced ( in 2014, accounting for 73% of China's total cotton production [18]. Meanwhile, surface water evaporation caused by high temperatures results in a severe water shortage in southern Xinjiang leading to soil salinization, a lowered survival rate for crops, and slow development of local agriculture [21]. Similarly, increased usage of underground water for irrigation exacerbates the soil salinization problems, which significantly reduce crop yield [10,11]. In this study, the application of surface water in both mixing ratio and round irrigation methods, significantly promotes dry matter accumulation (Fig. 2-3), NPK uptake (Fig. 4,5 and Table 5-8) and cotton yield (Fig. 6), compared with all other applied treatments. Our obtained results are in line with the findings of previous published literature [34,35,36]. The superiority of surface water over underground water in calcareous soil may likely be due to the following reasons; In line with the previous findings, in these experiments surface water application in both round and mixing ratio irrigation methods, significantly promotes dry matter accumulation ( Fig.   2-3), NPK uptake (Fig. 4,5 and Table 5-8) and cotton yield (Fig. 6), compared with all other applied treatments. The most likely reasons may be, in general surface water possess high temperature while the underground water temperature is quite low. Previous study has shown that well water irrigation with low temperature potentially inhibits the growth and development of jujube [22]. Likewise, several published literatures have shown that underground water irrigation (low temperature water) affect the growth, yield, dry matter accumulation and active developmental stages of grains plants such as peanuts, cucumber, and tomato [23,24,25,26].
For instance, a study conducted by Meng et al. (2016), noted that underground water irrigation significantly affects the growth and development of cotton plant. Similar results with the application of underground water irrigation is also obtained in this study. Furthermore, Deng et al., [27], also pointed out that underground water irrigation along with their low temperature properties significantly retarded the growth of vegetables and their photosynthetic developments.
Consequently, the excessive usage of underground water irrigation results in the accumulation of toxic substances in soil which alternatively leads to reduction in plants and grains yields [28,29].
The accumulation of salt can directly decrease soil nutrient efficiency by inhibiting microbial mineralization activity in soil [30]. Additionally, salinity can also indirectly affect soil nutrient cycling and efficiency by destroying soil physical structure [31,32,33]. On the flip side, Tthe study of Zzhang et al., 2002 [34] showed that alternate irrigation with surface fresh water can reduce soil salt content and increase cotton production which are in line with our findings. In this study surface water irrigation along with the different mixing ratios irrigation also shows promising effects on cotton yield and dry matter accumulation when compared with underground water treatment alone, this is possibly due to when the underground water and surface water were mixed together, the temperature and salt content were changed. For example, a study conducted by Tao et al. 2014 [35], showed that mixed irrigation mode of brackish and fresh water with a salinity of 1.6g/L could achieve higher crop yield with better quality. Consistently, a study carried out by Wang et al. 2010 [36], showed that well and canal mixed irrigation could keep the salt balance of root soil even in relatively dry years, while well irrigation alone results in salt accumulation in roots of winter wheat and decreased the yield up to 20% -30%. All these findings suggest that under-ground water irrigation possess negative effects on plant yield and growth whilst sur-face water irrigation and different mixing ratios irrigation significantly promote cotton yield NPK, uptake and dry matter accumulation.

Conclusions
It can be concluded that the application of surface water along with their different mixing ratios irrigation outcompete underground water irrigation in both mixing ratio and round applied irrigations methods. A significant highest The dry mater accumulation, nutrients uptake and cotton yield at various stages i.e., growth stage, boll stage, and boll opening stage were always noted significantly higher in surface water applied treatments compared with underground water treatment. Overall, our findings provide meaningful information to current irrigation practice in increasing cotton growth and yield. Therefore taken into account the scarcity of water resource We suggest that surface water irrigation application is recommended as an effective irrigation strategy in Xinjiang calcareous soil for better cotton yield and nutrient uptakes.

Listed responses to comments by the reviewers (PONE-D-22-03631)
Dear Prof. Dr. Rafiq Islam Academic Editor PLOS ONE, Many thanks for your letter. We greatly appreciate the constructive suggestions and comments on our MS entitled "Effect of surface water and underground water drip irrigation on Cotton growth and yield under two different irrigation schemes" from both yourself and the reviewers. All those comments are valuable and very helpful for us to improve our manuscript. We extend our great appreciation for taking the time and efforts to provide such insightful guidance. We have taken a complete consideration to all reviewers' comments as well as those suggestions from the editor's and have made the corrections one by one in the revised version of our manuscript. The changes in the revised MS are marked in track change model.
We sincerely hope the revised manuscript will be able to meet the requirement and will be finally accepted to publish on your journal of "PLOS ONE". Of course, we are always available to provide ongoing changes to our manuscript if there is any further request either from you or from the reviews.
Below please find the revised manuscript and the responses. Again, thank you and all the reviewers for your kinder assistance and we are looking forward to hearing from you at your earliest convenience. The following is a point-to-point response to the reviewers' comments.

Response to Reviewers
Comments from the editors and reviewers:

Response to the editors' comments
Editor's note: When submitting your revision, we need you to address these additional requirements.
Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming.
Response: Thank you very much, we have fully consider the PLOS ONE journal style requirements including file naming. Please see our revised manuscript We note that the grant information you provided in the 'Funding Information' and 'Financial Disclosure' sections do not match.
When you resubmit, please ensure that you provide the correct grant numbers for the awards you received for your study in the 'Funding Information' section.
Response: We are extremely sorry for our careless job. We have now provided the corrected and Please see our revised funding Information section in our revised manuscript.
We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide.
Response: Thank you very much, Actually we don't have any repository data information, and we don't want to provide any repository information, so therefore please update our data availability statement to no repository data availability statement.
Please include your tables as part of your main manuscript and remove the individual files. Please note that supplementary tables (should remain/ be uploaded) as separate "Supporting Information" files.
Response: Thank you very much. We have included the tables as a part of manuscript. Please check our revised manuscript.
Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement.
Response: Thank you so much for your time. We have removed the funding-related text from the manuscript. Please check our revised manuscript.
Please state what role the funders took in the study. If the funders had no role, please state: "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript." If this statement is not correct you must amend it as needed.
Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf." Response: Thank you so very much. "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript." If any authors received a salary from any of your funders, please state which authors and which funders.
Response: Thank you very much for time. "The authors received no specific funding for this work." The following is a point-to-point response to the reviewers' comments.
Reviewer(s)' Comments to Author:

Reviewer:
Major Issues/Concerns Response to reviewer # 1: Thank you very much. We appreciate you taking the time to offer us your comments and insights related to the paper. We found your feedback very constructive. We tried to be responsive to your concerns. We hope you find these revisions rise to your expectations.
Regarding Reviewer#1 major concerns, we make an explanation in detail as follow: 1. "Badly unclear written. Revise it as I revised for the first experiment." Response: Thank you very much for your kind revision. We have revised experiment 2 nd , according to the reviewer suggestion. For instance "The first experiment comprised of five ratios of underground water to surface water including; 1:0 (U), 0:1 (S), 1:1 (T3), 1:2 (T4) and 1:3 (T5). Response: Many thanks. Basically in this sentence {"Furthermore, two-way ANOVAs revealed a significant main and interactive effect on dry matter accumulation at various growth stages treated with surface water in round irrigation scheme (p < 0.05)"} we present the results of two way ANOVA for which after coding the data in experiment 2 nd , we consider Surface water (S) as a separate factor and underground water (U) as a separate factor while the S*U is their interactive factor, To be more clear and precise following is the ANOVA tables for Surface water, Underground water and their interaction for various growth stages, but in our manuscript we have linked these ANOVA tables results with their corresponding figures. Please see figure 3 Table: Results of two-way ANOVAs for growth stages (stem, leaves and roots) of dry matter accumulation as dependent on surface water (S), underground water (U) and their interaction (S× U).

Stem
Leaves Roots